The present invention relates to a method for purifying underground water which is contaminated with anthropogeneous pollutants or has been polluted by underground leaching.
A known method of purification of contaminated underground water, described in Russian Patent No. 1838598, Cl. CO2F3/34, 1993, comprises injecting cultured fluid having sulfate reducing bacteria and an organic nutrient source into the contaminated water. The purification efficiency obtained by this method is low.
Another method of purification of contaminated underground water is described in Russian Patent No. 2107042, issued Mar. 20, 1998), and comprises the steps of characterizing the soil composition at the location of the contaminated water, taking a sample of the contaminated underground water from one or more wells at the location of contaminated water, characterizing the concentrations of contaminants in the collected sample, introducing into the sample a nutrient environment comprising mineral and organic components to effect the growth of sulfate reducing bacteria, accumulating a biomass of selected sulfate reducing bacteria, and introducing the biomass into the contaminated water via one or more wells at the location of the contaminated water.
The above-noted purification method, however, suffers from low efficiency since favorable conditions do not exist to promote the activity of the sulfate reducing bacteria. Also, significant expenditures are incurred due to the number of wells involved and the costs of accumulating the biomass.
The present invention provides a solution to the problem of improving the purification efficiency of a contaminated underground water purification method by a shortening of the time for the sulfate reducing bacteria to effect its activity, thereby reducing operating costs.
The purification method of the present invention comprises the steps of characterizing the soil composition at the location of the contaminated water, taking a sample of the contaminated underground water from one or more wells at the location of contaminated water, characterizing the concentrations of contaminants in the collected sample, introducing into the sample a nutrient environment comprising mineral and organic components to effect the growth of sulfate reducing bacteria, accumulating a biomass of selected sulfate reducing bacteria, and introducing the biomass into the contaminated water via one or more wells at the location of the contaminated water, and further comprises the step of sampling an anthropogeneous contaminant and introducing ferri-compounds into at least one well in response to an assessment of the anthropogeneous contaminant sampling. At least one anthropogeneous contaminant sample is drawn of the respective underground water and from background or reference underground water and soil components. The drawn samples are blended or otherwise permitted to mix and, at a predetermined time, a determination is made of the concentrations of contaminating components comprised in the blended mixture. The concentrations of the contaminating components comprised in the blended mixture are compared to the same respective concentrations of these contaminating components in the sample of the contaminated underground water. Conclusions are then drawn from this comparison of the contaminating components of the blended sample mixture and the contaminated underground water sample with respect to the biomass consumption and the number of wells which are to be involved in the purification operation. In connection with these conclusions, in the event that a proportion of the concentrations of the contaminating components of the blended sample mixture and the contaminated underground water sample exceeds one, the biomass consumption and the number of wells are increased and the addition of a ferri-compound is made to at least one of the wells to create negative values of redox potential. The organic component of the nutrient environment is comprised of series formed by an aqueous solution of clay having a ratio of solids to liquids between 0.001 to 0.003, an aqueous solution of natural carbohydrate polymers at a ratio of solids to liquids between 0.001 to 0.005, or a mixture of such components and higher carbohydrate polymers. The series of higher carbohydrate polymers are formed of vegetative residues, wood sawdust, cane, sedge, and domestic waste.
The method of the present invention enhances the efficiency of the purification operation in that the logarithmic stage of the sulfate reducing bacteria vital activity is shortened and fewer wells are otherwise involved in the purification operation. The ferri-compound creates favorable redox conditions (potential) for vital activity of the sulfate reducing bacteria (SRB).